A catalyst for preparing 1,6-hexanediol by hydrogenating dimethyl adipate, a preparation method and application thereof

Abstract

The application provides a catalyst for preparing 1,6-hexanediol by hydrogenating dimethyl adipate, which is composed of three non-noble metal elements of Cu, Zn and Mo, wherein the molar ratio of copper and zinc is Cu:Zn=1:(0.6-1.5); and the molar amount of molybdenum is 0.2%-1.5% of the sum of the molar amounts of copper and zinc. The catalyst is synthesized by a co-precipitation method to obtain Mo-doped CuZn basic carbonate in one step, and is obtained by calcination and activation. The application also provides application of the catalyst in preparation of 1,6-hexanediol by hydrogenating dimethyl adipate. The catalyst has high catalytic activity, and the obtained product 1,6-hexanediol has high selectivity, excellent cycle stability and simple preparation process. The catalyst can greatly reduce the reaction temperature and pressure in the reaction process, and can solve the problems of high pressure and high energy consumption in the industrial reaction process, and can reduce the difficulty of subsequent separation and purification of the 1,6-hexanediol product.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and particularly to a hydrogenation catalyst for the production of 1,6-hexanediol from dimethyl adipate and its preparation method. Background Technology

[0002] 1,6-Hexanediol is widely used in the production of polyesters, polyurethanes, coil coatings, UV curing agents, pharmaceutical intermediates, and pesticides. The hydrogenation synthesis method using adipic acid and its derivatives is currently the most mature and complete industrial route for synthesizing 1,6-hexanediol. Compared to the direct hydrogenation of adipic acid, this process for preparing 1,6-hexanediol via the hydrogenation of dimethyl adipic acid ester reduces reaction difficulty while achieving higher selectivity for 1,6-hexanediol.

[0003] Noble metal catalysts have been used in the hydrogenation of dimethyl adipate (DMA) to prepare 1,6-hexanediol (1,6-HDO). Patent 201110347496.6 describes using any one of the noble metals Ru, Pd, and Rh as the main catalyst, and adding one or more of Ir, Co, Cu, Ni, Fe, and Sn as co-catalysts, supported on alumina, silica, titanium dioxide, or other materials. Under conditions of 100–200 °C and a hydrogen pressure of 1–3 MPa for 5–12 h, a DMA conversion of 60.0–99.9% and a 1,6-HDO selectivity of 70.0–99.9% can be achieved. Patent 201611134027.5 utilizes a carbon-supported gold-platinum nanoparticle noble metal catalyst, achieving a DMA conversion rate exceeding 99% and a 1,6-HDO selectivity under conditions of 170–180℃ and 2.5–5 MPa hydrogen pressure. Patent 202010433632.2 mentions a supported noble metal catalyst with ruthenium or iridium as the active component, copper chromite as the promoter, and lanthanum-doped SiO2 or ZrO2 as the support, achieving a DMA conversion rate of 92% and a 1,6-HDO selectivity of 94% at 150℃ and 2.5 MPa pressure. Noble metal catalysts exhibit high catalytic performance, achieving high conversion rates and 1,6-HDO selectivity at relatively low reaction temperatures and hydrogen pressures. However, the scarcity of noble metal resources leads to high catalyst production costs, thus hindering large-scale industrial applications.

[0004] In non-precious metal research, patent 03137601.0 uses a four-component CuO-ZnO-Al2O3-BaO catalyst, achieving a DMA conversion rate of 99.1% and a 1,6-HDO selectivity of 97.8% at a reaction temperature of 220℃ and a hydrogen pressure of 7.9 MPa. However, the reaction temperature and pressure are high. Patent 201710236004.3 mentions a non-precious metal supported Cu / SiO2 catalyst prepared by ammonia evaporation, which can achieve a DMA conversion rate greater than 98% at a reaction temperature of 225℃ and a hydrogen pressure of 3 MPa, but the 1,6-HDO selectivity is low (approximately 88%), and the reaction temperature is also high. Yang Xingchuan et al. reported that a non-precious metal CuZnAl catalyst, under a hydrogen pressure of 27.0 MPa and a reaction temperature of 280℃ for 5 h, achieved a DMA conversion of 94.05% but a 1,6-HDO selectivity of only 74.88% (Research on the Catalytic Hydrogenation of Dimethyl Adipate to 1,6-Hexanediol, Journal of Yellow River Conservancy Technical Institute, Vol. 26, No. 4). Liu Shulin et al. mentioned a CuAl5 / SBA-15 catalyst that achieved an HDO yield of 87.05% under a reaction temperature of 240℃, a reaction pressure of 6 MPa, and a reaction time of 6 h (Al-doped Cu / SBA-15 Catalyst for the Hydrogenation of Dimethyl Adipate to 1,6-Hexanediol, Chemical Industry and Engineering Progress, Vol. 42, No. 1, 2023). Therefore, it is evident that currently developed non-precious metal catalysts require relatively high reaction temperatures and hydrogen pressures to achieve high reaction conversion rates and 1,6-HDO selectivity. High temperature and high pressure, especially high pressure reaction conditions, place extremely high demands on the reaction equipment, increase production costs, and bring greater safety hazards; moreover, high temperature conditions can easily lead to the formation of a variety of by-products, which greatly increases the difficulty of subsequent separation and purification of 1,6-HDO products. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol, its preparation method, and its application. The catalyst of this invention exhibits high catalytic activity, high selectivity for the 1,6-hexanediol product, excellent cycle stability, and a simple preparation process. All active components of the catalyst are non-precious metals, resulting in low catalyst preparation costs. The catalyst involved in this invention demonstrates excellent performance during the reaction process, significantly reducing reaction temperature and pressure. This solves the problems of high temperature, high pressure, and high energy consumption in industrial reactions while simultaneously reducing the difficulty of purifying the subsequent 1,6-hexanediol product.

[0006] To achieve the above-mentioned objectives, the technical solution of this invention is as follows:

[0007] This invention provides a catalyst for the hydrogenation of dimethyl adipate to prepare 1,6-hexanediol, which is composed of three non-noble metal elements: Cu, Zn, and Mo. The molar ratio of copper to zinc is Cu:Zn = 1:(0.6-1.5), and the molar amount of molybdenum is 0.2% to 1.5% of the sum of the molar amounts of copper and zinc.

[0008] Preferably, the molar ratio of copper to zinc is Cu:Zn=1:(0.8-1.1), and the molar amount of molybdenum is 0.5% to 1.2% of the sum of the molar amounts of copper and zinc.

[0009] A more preferred ratio is a copper:zinc molar ratio of Cu:Zn=1:1, and a molar amount of molybdenum of 0.5% to 1.0% of the sum of the copper and zinc molar amounts.

[0010] This invention also provides a method for preparing a catalyst for the hydrogenation of dimethyl adipic acid to 1,6-hexanediol. The method involves a one-step co-precipitation synthesis of Mo-doped CuZn basic carbonate, followed by calcination and activation to obtain the CuZnMo composite catalyst. Specific steps include:

[0011] 1) Prepare aqueous solutions of copper, zinc, and molybdenum metal salts, with a molar ratio of copper to zinc of 1:(0.6-1.5) and a molar amount of molybdenum of 0.2% to 1.5% of the sum of the molar amounts of copper and zinc; prepare an aqueous solution of sodium carbonate, with the amount of sodium carbonate being 1.0 to 1.1 times the total molar amount of Cu, Zn, and Mo metal salts; heat the two aqueous solutions separately to 60℃ to 65℃, then mix the two aqueous solutions and react them with stirring for 2 to 3 hours, separating the Mo-doped CuZn basic carbonate and drying it;

[0012] 2) The dried Mo-doped CuZn basic carbonate was calcined at 200℃~250℃ for 4~5 h to obtain the catalyst precursor;

[0013] 3) Activate the catalyst precursor in H2 atmosphere at an activation temperature of 200℃~250℃ for 1~4 h; cool to room temperature to obtain CuZnMo composite catalyst.

[0014] Preferably, the Cu and Zn metal salts include water-soluble metal salts such as their metal nitrates, metal sulfates, and metal chlorides; the Mo metal salt is selected from ammonium molybdate.

[0015] More preferably, the Cu and Zn metal salts are copper nitrate and zinc nitrate.

[0016] Preferably, the catalyst is used in the hydrogenation of dimethyl adipate to prepare 1,6-hexanediol.

[0017] Preferably, the reaction temperature is 140℃~180℃ and the reaction hydrogen pressure is 2~5 MPa.

[0018] Preferably, the room temperature is generally 10℃~30℃.

[0019] The present invention also provides a method for improving the catalytic effect of non-precious metal catalyst in the hydrogenation of dimethyl adipate to 1,6-hexanediol, wherein the non-precious metal catalyst is a copper-zinc catalyst, and non-precious metal molybdenum is added to the copper-zinc catalyst, wherein the molar amount of molybdenum is 0.2% to 1.5% of the sum of the molar amounts of copper and zinc.

[0020] The molar ratio of copper to zinc in the copper-zinc catalyst is Cu:Zn=1:(0.6-1.5), more preferably, the molar ratio of copper to zinc in the copper-zinc catalyst is Cu:Zn=1:(0.8-1.1), and even more preferably, the molar ratio of copper to zinc is Cu:Zn=1:1.

[0021] Preferably, the molar amount of molybdenum is 0.5% to 1.2% of the sum of the molar amounts of copper and zinc, and more preferably, the proportion is 0.5% to 1.0%.

[0022] The present invention will be further explained and described below:

[0023] This invention employs a co-precipitation method to synthesize Mo-doped CuZn basic carbonate in one step, followed by calcination and reduction activation at a lower temperature. This yields a CuZnMo ternary metal composite catalyst with strong catalytic activity for the hydrogenation of dimethyl adipate to 1,6-hexanediol, enabling the reaction to proceed under lower reaction temperatures and pressures, thereby significantly improving the conversion rate and the selectivity of the product 1,6-hexanediol.

[0024] The catalyst obtained above was used to catalyze the hydrogenation of dimethyl adipate to 1,6-hexanediol. The process is as follows: A certain amount of dimethyl adipate, catalyst, and 1,4-dioxane solvent were added to a reaction vessel. The mixture was heated to the reaction temperature and then hydrogen gas was introduced to initiate the reaction. The reaction temperature was 140-180℃, and the hydrogen pressure was 2-5 MPa. After the reaction was completed, the temperature was lowered, the catalyst was separated, and the reaction solution was collected for analysis. The reaction products were quantitatively analyzed using gas chromatography with internal standard method.

[0025] The core improvements in this application are:

[0026] This invention provides a method for preparing a CuZnMo ternary metal composite catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol. A very small amount of metallic Mo is introduced into the CuZn metal to increase the catalyst's adsorption and activation ability for the C=O bonds in dimethyl adipate; the introduction of Mo can increase the oxygen vacancy content of the catalyst and regulate the Cu... + With Cu 0By adjusting the proportions of different metal components and performing calcination and reduction activation at low temperatures, a CuZnMo ternary metal composite catalyst with high activity and selectivity was prepared. This resulted in high conversion rates and high selectivity for the hydrogenation of dimethyl adipate to 1,6-hexanediol under low-temperature and low-pressure reaction conditions. (Appendix) Figure 1 and Figure 2 The results of characterization and analysis of the physicochemical properties of the catalyst are presented.

[0027] Compared with the prior art, the advantages of the present invention are:

[0028] 1. This invention provides a method for preparing a CuZnMo ternary metal composite catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol. The CuZnMo ternary metal composite catalyst exhibits high catalytic activity, strong stability, and high selectivity for 1,6-hexanediol. Since no precious metals are involved in the active component of the catalyst, it can significantly reduce the production cost. Compared with existing preparation methods, no additional steps are added, and the calcination and activation processes involve lower temperatures, effectively reducing energy consumption in the catalyst production process and enabling industrial-scale production.

[0029] 2. The CuZnMo ternary metal composite catalyst prepared in this invention is used to catalyze the hydrogenation of dimethyl adipate to 1,6-hexanediol. Under reaction conditions of 140-180℃ and hydrogen pressure of 2-5 MPa, the conversion rate of dimethyl adipate is high, generally above 99.1%, and can reach up to 100%; the selectivity of 1,6-hexanediol is high, generally above 99.0%, and can reach up to 99.7%. The mild reaction conditions not only effectively reduce the requirements for production equipment in industrial reactions and reduce fixed asset investment, but also reduce energy and material consumption, improve the selectivity of 1,6-hexanediol reaction, and greatly reduce the difficulty of subsequent purification of 1,6-hexanediol products.

[0030] 3. The CuZnMo ternary metal composite catalyst prepared by this invention has good recycling performance and still maintains good catalytic performance after 10 cycles.

[0031] The catalytic performance and structure of the catalyst of the present invention will be further described below with reference to specific embodiments and accompanying drawings. Attached Figure Description

[0032] Figure 1 HRTEM image and elemental mapping diagram of CuZnMo catalyst; Figure 1 It can be seen that the three metals Cu, Zn and Mo are highly dispersed in the prepared CuZnMo catalyst.

[0033] Figure 2Fine O1s spectra and Cu Auger spectra of CuZn and CuZnMo catalysts; Figure 2 The 1s spectrum of O in the catalyst unwraps into three peaks at binding energies of 530.1, 531.7, and 533.0 eV, corresponding to lattice oxygen (O) in the catalyst. L ), surface oxygen vacancies (O v ) and adsorbed oxygen (O ad It can be clearly seen that O in the catalyst after the introduction of Mo is reduced. ad and O L The peak area is significantly reduced relative to the O v The peak area is relatively larger. v The increased content leads to a stronger electron transfer interface between Mo, Zn, O, and Cu, enhancing the catalyst's hydrogenation capacity. The Cu LMM Auger spectra with peaks at binding energies of 916.4, 917.6, and 918.9 eV belong to Cu... + Cu 2+ Cu 0 The fitting graph shows that the Cu in the catalyst increases after introducing a small amount of Mo. 2+ The relative peak area remained essentially unchanged, while Cu 0 The relative peak area is significantly reduced, Cu + The relative peak area increases (Cu) + / Cu 0 (Increased from 0.74 to 1.40). Mo versus Cu + With Cu 0 Adjusting the ratio enhances the hydrogenation capacity and selectivity of the catalyst. Detailed Implementation

[0034] Example 1

[0035] 4.46 g of copper nitrate, 6.74 g of zinc nitrate hexahydrate, and 0.12 g of ammonium molybdate were dissolved in deionized water and heated to 60°C. Separately, 5.71 g of sodium carbonate was dissolved in deionized water and heated to 65°C. The two aqueous solutions were mixed under vigorous stirring. The reaction was carried out at 65°C for 2 hours, and the precipitate was separated and dried at 120°C. The precipitate was then placed in a muffle furnace and calcined at 240°C for 4 hours. After cooling to room temperature, the catalyst precursor was obtained. Catalyst activation: The catalyst precursor was placed in a tube furnace and activated at 250°C for 2 hours under a H2 atmosphere. After nitrogen protection and cooling to room temperature, the CuZnMo catalyst was obtained, with a copper:Zn molar ratio of Cu:Zn = 1:0.95 and a Mo content of 0.2% of the sum of the copper and zinc molar amounts.

[0036] The catalyst prepared above was used in the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol. The specific reaction process is as follows: 5 g of dimethyl adipate, 50 ml of 1,4-dioxane, and 2.5 g of catalyst were added to the reactor. The reactor was sealed, and nitrogen was introduced to replace the air inside. The temperature was raised to the set reaction temperature of 180°C, and then hydrogen was introduced to the set pressure of 5 MPa. Stirring was started, and the reaction was maintained at constant temperature and pressure for 5 hours. After the reaction was completed, the temperature was lowered to room temperature, the catalyst was separated, and the gas chromatography analysis of the reaction liquid showed a conversion rate of 99.6% and a selectivity of 99.1% for 1,6-hexanediol.

[0037] Example 2

[0038] 3.65 g of copper sulfate pentahydrate, 5.65 g of zinc nitrate hexahydrate, and 0.33 g of ammonium molybdate were dissolved in deionized water and heated to 62°C. Separately, 4.5 g of sodium carbonate was dissolved in deionized water and heated to 63°C. The two aqueous solutions were mixed under vigorous stirring. The reaction was carried out at 63°C for 2.5 h, and the precipitate was separated and dried at 120°C. The precipitate was then placed in a muffle furnace and calcined at 220°C for 4 h. After cooling to room temperature, the catalyst precursor was obtained. Catalyst activation: The catalyst precursor was placed in a tube furnace and activated at 250°C for 3.5 h under H2 atmosphere. After nitrogen protection and cooling to room temperature, the CuZnMo catalyst was obtained, with a copper:Zn molar ratio of Cu:Zn = 1:1.3 and a Mo content of 0.8% of the sum of the copper and zinc molar amounts.

[0039] The catalyst prepared above was used in the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol. The specific reaction process is as follows: 4 g of dimethyl adipate, 40 ml of 1,4-dioxane, and 2 g of catalyst were added to the reactor. The reactor was sealed, and nitrogen was introduced to replace the air inside. The temperature was raised to the set reaction temperature of 180°C, and then hydrogen was introduced to the set pressure of 4 MPa. Stirring was started, and the reaction was maintained at constant temperature and pressure for 7 hours. After the reaction was completed, the temperature was lowered to room temperature, the catalyst was separated, and gas chromatography analysis showed a reaction conversion rate of 99.4% and a 1,6-hexanediol selectivity of 99.0%.

[0040] Example 3

[0041] 2.82 g of copper nitrate, 4.46 g of zinc nitrate hexahydrate, and 0.38 g of ammonium molybdate were dissolved in deionized water and heated to 65°C. Separately, 3.84 g of sodium carbonate was dissolved in deionized water and heated to 60°C. The two aqueous solutions were mixed under vigorous stirring. The reaction was carried out at 64°C for 3 hours, and the precipitate was separated and dried at 120°C. The precipitate was then calcined in a muffle furnace at 250°C for 4 hours. After cooling to room temperature, the catalyst precursor was obtained. Catalyst activation: The catalyst precursor was placed in a tube furnace and activated at 230°C for 4 hours under a H2 atmosphere. After cooling to room temperature under nitrogen protection, the CuZnMo catalyst was obtained, with a copper:Zn molar ratio of Cu:Zn = 1:1 and a Mo content of 1% of the sum of the copper and zinc molar amounts.

[0042] The catalyst prepared above was used in the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol. The specific reaction process is as follows: 3 g of dimethyl adipate, 30 ml of 1,4-dioxane, and 1.5 g of catalyst were added to the reactor. The reactor was sealed, and nitrogen was purged to replace the air inside. The temperature was raised to the set reaction temperature of 180°C, and then hydrogen was introduced to the set pressure of 3 MPa. Stirring was started, and the reaction was maintained at constant temperature and pressure for 10 hours. After the reaction was completed, the temperature was lowered to room temperature, the catalyst was separated, and gas chromatography analysis showed a conversion rate of 99.9% and a selectivity of 99.7% for 1,6-hexanediol.

[0043] Example 4

[0044] 3.31 g of copper nitrate, 3.05 g of zinc sulfate heptahydrate, and 0.52 g of ammonium molybdate were dissolved in deionized water and heated to 65°C. Separately, 3.81 g of sodium carbonate was dissolved in deionized water and heated to 65°C. The two aqueous solutions were mixed under vigorous stirring. The reaction was carried out at 65°C for 2.5 h, and the precipitate was separated and dried at 120°C. The precipitate was then placed in a muffle furnace and calcined at 250°C for 4 h. After cooling to room temperature, the catalyst precursor was obtained. Catalyst activation: The catalyst precursor was placed in a tube furnace and activated at 250°C for 2 h under a H2 atmosphere. After cooling to room temperature under nitrogen protection, the CuZnMo catalyst was obtained, with a copper:Zn molar ratio of Cu:Zn = 1:0.6 and a Mo content of 1.5% of the sum of the copper and zinc molar amounts.

[0045] The catalyst prepared above was used in the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol. The specific reaction process is as follows: 5 g of dimethyl adipate, 50 ml of 1,4-dioxane, and 2.5 g of catalyst were added to the reactor. The reactor was sealed, and nitrogen was purged to replace the air inside. The temperature was raised to the set reaction temperature of 180°C, and then hydrogen was introduced to the set pressure of 5 MPa. Stirring was started, and the reaction was maintained at constant temperature and pressure for 7 hours. After the reaction was completed, the temperature was lowered to room temperature, the catalyst was separated, and gas chromatography analysis showed a reaction conversion rate of 99.1% and a 1,6-hexanediol selectivity of 99.0%.

[0046] Example 5

[0047] 3.10 g of copper nitrate, 4.46 g of zinc nitrate hexahydrate, and 0.39 g of ammonium molybdate were dissolved in deionized water and heated to 65°C. Separately, 3.95 g of sodium carbonate was dissolved in deionized water and heated to 65°C. The two aqueous solutions were mixed under vigorous stirring. The reaction was carried out at 65°C for 2.5 h, and the precipitate was separated and dried at 120°C. The precipitate was then calcined in a muffle furnace at 200°C for 5 h, and cooled to room temperature to obtain the catalyst precursor. Catalyst activation: The catalyst precursor was placed in a tube furnace and activated at 250°C for 2 h under H2 atmosphere. After purging with nitrogen and cooling to room temperature, the CuZnMo catalyst was obtained, with a copper:Zn molar ratio of Cu:Zn = 1:0.9 and a Mo content of 1% of the sum of the copper and zinc molar amounts.

[0048] The catalyst prepared above was used in the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol. The specific reaction process is as follows: 2.5 g of dimethyl adipate, 25 ml of 1,4-dioxane, and 1 g of catalyst were added to the reactor. The reactor was sealed, and nitrogen was introduced to replace the air inside. The temperature was raised to the set reaction temperature of 180°C, and then hydrogen was introduced to the set pressure of 2 MPa. Stirring was started, and the reaction was maintained at constant temperature and pressure for 12 hours. After the reaction was completed, the temperature was lowered to room temperature, the catalyst was separated, and gas chromatography analysis showed a reaction conversion rate of 99.6% and a 1,6-hexanediol selectivity of 99.1%.

[0049] Example 6

[0050] 2.81 g of copper nitrate, 4.98 g of zinc nitrate hexahydrate, and 0.48 g of ammonium molybdate were dissolved in deionized water and heated to 65°C. Separately, 3.95 g of sodium carbonate was dissolved in deionized water and heated to 65°C. The two aqueous solutions were mixed under vigorous stirring. The reaction was carried out at 65°C for 2.5 h, and the precipitate was separated and dried at 120°C. The precipitate was then placed in a muffle furnace and calcined at 250°C for 4.5 h. After cooling to room temperature, the catalyst precursor was obtained. Catalyst activation: The catalyst precursor was placed in a tube furnace and activated at 200°C for 4 h under H2 atmosphere. After nitrogen protection and cooling to room temperature, the CuZnMo catalyst was obtained, with a copper:Zn molar ratio of Cu:Zn = 1:1.1 and a Mo content of 1.2% of the sum of the copper and zinc molar amounts.

[0051] The catalyst prepared above was used in the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol. The specific reaction process is as follows: 5 g of dimethyl adipate, 50 ml of 1,4-dioxane, and 2.5 g of catalyst were added to the reactor. The reactor was sealed, and nitrogen was introduced to replace the air inside. The temperature was raised to the set reaction temperature of 160°C, and then hydrogen was introduced to the set pressure of 5 MPa. Stirring was started, and the reaction was maintained at constant temperature and pressure for 10 hours. After the reaction was completed, the temperature was lowered to room temperature, the catalyst was separated, and gas chromatography analysis showed a reaction conversion rate of 99.8% and a 1,6-hexanediol selectivity of 99.3%.

[0052] Example 7

[0053] 3.75 g of copper nitrate, 4.76 g of zinc nitrate hexahydrate, and 0.45 g of ammonium molybdate were dissolved in deionized water and heated to 65°C. Separately, 4.43 g of sodium carbonate was dissolved in deionized water and heated to 65°C. The two aqueous solutions were mixed under vigorous stirring. The reaction was carried out at 65°C for 2 h, and the precipitate was separated and dried at 120°C. The precipitate was then placed in a muffle furnace and calcined at 250°C for 5 h. After cooling to room temperature, the catalyst precursor was obtained. Catalyst activation: The catalyst precursor was placed in a tube furnace and activated at 230°C for 2.5 h under a H2 atmosphere to obtain the CuZnMo catalyst. The molar ratio of copper to zinc was Cu:Zn = 1:0.8, and the Mo content of the catalyst was 1% of the sum of the molar amounts of copper and zinc.

[0054] The catalyst prepared above was used in the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol. The specific reaction process is as follows: 3 g of dimethyl adipate, 30 ml of 1,4-dioxane, and 1 g of catalyst were added to the reactor. The reactor was sealed, and nitrogen was introduced to replace the air inside. The temperature was raised to the set reaction temperature of 180°C, and then hydrogen was introduced to the set pressure of 3 MPa. Stirring was started, and the reaction was maintained at constant temperature and pressure for 12 hours. After the reaction was completed, the temperature was lowered to room temperature, the catalyst was separated, and gas chromatography analysis showed a reaction conversion rate of 99.8% and a 1,6-hexanediol selectivity of 99.5%.

[0055] Example 8

[0056] 1.88 g of copper nitrate, 4.46 g of zinc nitrate hexahydrate, and 0.31 g of ammonium molybdate were dissolved in deionized water and heated to 65°C. Separately, 3.21 g of sodium carbonate was dissolved in deionized water and heated to 60°C. The two aqueous solutions were mixed under vigorous stirring. The reaction was carried out at 64°C for 3 h, and the precipitate was separated and dried at 120°C. The precipitate was then placed in a muffle furnace and calcined at 240°C for 4 h. After cooling to room temperature, the catalyst precursor was obtained. Catalyst activation: The catalyst precursor was placed in a tube furnace and activated at 250°C for 3.5 h under a H2 atmosphere to obtain the CuZnMo catalyst. The molar ratio of copper to zinc was Cu:Zn = 1:1.5, and the Mo content of the catalyst was 1% of the sum of the molar amounts of copper and zinc.

[0057] The catalyst prepared above was used in the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol. The specific reaction process is as follows: 5 g of dimethyl adipate, 50 ml of 1,4-dioxane, and 1.5 g of catalyst were added to the reactor. The reactor was sealed, and nitrogen was purged to replace the air inside. The temperature was raised to the set reaction temperature of 140°C, and then hydrogen was introduced to the set pressure of 5 MPa. Stirring was started, and the reaction was maintained at constant temperature and pressure for 15 hours. After the reaction was completed, the temperature was lowered to room temperature, the catalyst was separated, and gas chromatography analysis showed a conversion rate of 99.7% and a selectivity of 99.2% for 1,6-hexanediol.

[0058] Example 9

[0059] 2.81 g of copper nitrate and 4.46 g of zinc nitrate hexahydrate were dissolved in deionized water and heated to 60°C. Separately, 3.71 g of sodium carbonate was dissolved in deionized water and heated to 60°C. The two aqueous solutions were mixed under vigorous stirring. The reaction was carried out at 62°C for 3 h, and the precipitate was separated and dried at 120°C. The precipitate was then placed in a muffle furnace and calcined at 250°C for 4 h. After cooling to room temperature, a catalyst precursor was obtained. Catalyst activation: The catalyst precursor was placed in a tube furnace and activated at 250°C for 2 h under a H2 atmosphere to obtain a Mo-free CuZn catalyst with a copper:Zn molar ratio of Cu:Zn = 1:1. Using this catalyst, the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol was catalyzed according to the reaction process and conditions described in Example 3. Gas chromatography analysis showed a conversion rate of 93.0% and a 1,6-hexanediol selectivity of 89.6%.

[0060] Example 10

[0061] 3.75 g of copper nitrate and 4.76 g of zinc nitrate hexahydrate were dissolved in deionized water and heated to 62°C. Separately, 4.38 g of sodium carbonate was dissolved in deionized water and heated to 65°C. The two aqueous solutions were mixed under vigorous stirring. The reaction was carried out at 65°C for 2 h, and the precipitate was separated and dried at 120°C. The precipitate was then placed in a muffle furnace and calcined at 250°C for 5 h. After cooling to room temperature, a catalyst precursor was obtained. Catalyst activation: The catalyst precursor was placed in a tube furnace and activated at 250°C for 3 h under H2 atmosphere to obtain a Mo-free CuZn catalyst with a copper:Zn molar ratio of Cu:Zn = 1:0.8. Using this catalyst, the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol was catalyzed according to the reaction process and conditions described in Example 7. Gas chromatography analysis showed a conversion rate of 89.5% and a 1,6-hexanediol selectivity of 90.4%.

[0062] Example 11

[0063] Similarly, when preparing the aqueous solutions of metal salts and sodium carbonate, 1.88 g of copper nitrate, 4.46 g of zinc nitrate hexahydrate, and 3.21 g of sodium carbonate were weighed. The remaining steps were consistent with Example 8 to obtain a Mo-free CuZn catalyst, with a copper:Zn molar ratio of Cu:Zn = 1:1.5. Using this catalyst, the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol was catalyzed according to the reaction process and conditions described in Example 8. Gas chromatography analysis showed a conversion rate of 87.2% and a 1,6-hexanediol selectivity of 85.6%.

[0064] Example 12

[0065] Similarly, when preparing the aqueous solutions of metal salts and sodium carbonate, 5.25 g of copper nitrate, 8.34 g of zinc nitrate hexahydrate, 2.10 g of ammonium molybdate, and 6.84 g of sodium carbonate were weighed. The remaining steps were consistent with Example 3 to obtain a CuZnMo catalyst with a copper:Zn molar ratio of Cu:Zn = 1:1 and a Mo content of 3% of the sum of the copper and zinc molar amounts. Using this catalyst, the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol was catalyzed according to the reaction process and conditions described in Example 3. Gas chromatography analysis showed a conversion rate of 82.1% and a 1,6-hexanediol selectivity of 84.0%.

[0066] Example 13

[0067] In the catalyst preparation process, the calcination temperature was increased from 200℃ in Example 5 to 350℃, while the remaining steps remained the same as in Example 5. This yielded a CuZnMo catalyst prepared at 350℃ with a copper:Zn molar ratio of Cu:Zn = 1:0.9 and a Mo content of 1%. Using this catalyst, the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol was catalyzed according to the reaction process and conditions described in Example 5. Gas chromatography analysis showed a conversion rate of 92.1% and a 1,6-hexanediol selectivity of 89.2%.

[0068] Example 14

[0069] In the catalyst preparation process, the activation temperature was increased from 200℃ in Example 6 to 350℃, while the remaining steps remained the same as in Example 6. This yielded a CuZnMo catalyst prepared by reduction activation at 350℃, with a copper:zinc molar ratio of Cu:Zn = 1:1.1 and a Mo content of 1.2% equal to the sum of the copper and zinc molar amounts. Using this catalyst, the liquid-phase hydrogenation of dimethyl adipate to 1,6-hexanediol was catalyzed according to the reaction process and conditions described in Example 6. Gas chromatography analysis showed a conversion rate of 95.0% and a 1,6-hexanediol selectivity of 91.0%.

[0070] Example 15

[0071] The CuZnMo catalyst with a Mo content of 1% prepared in Example 3 was reacted according to the reaction process and conditions described in Example 1. After catalyst separation, it was directly used in the next batch of reaction to evaluate the cyclic stability of the catalyst. The evaluation results are shown in Table 1 below:

[0072] Table 1 Cyclic stability evaluation results

[0073]

[0074] The above description is a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the claims of the present invention.

Claims

1. The application of a catalyst in the hydrogenation of dimethyl adipate to 1,6-hexanediol, characterized in that: The catalyst is composed of three non-precious metal elements: Cu, Zn, and Mo. The molar ratio of copper to zinc is Cu:Zn = 1:(0.6-1.5); the molar amount of molybdenum is 0.2% to 1.5% of the sum of the molar amounts of copper and zinc. The catalyst is obtained by one-step synthesis of Mo-doped CuZn basic carbonate via co-precipitation, followed by calcination and activation. It is referred to as the CuZnMo composite catalyst. Specific steps include: 1) Prepare aqueous solutions of copper, zinc, and molybdenum metal salts, with a molar ratio of copper to zinc of 1:(0.6-1.5) and a molar amount of molybdenum of 0.2% to 1.5% of the sum of the molar amounts of copper and zinc; prepare an aqueous solution of sodium carbonate, with the amount of sodium carbonate being 1.0 to 1.1 times the total molar amount of Cu, Zn, and Mo metal salts; heat the two aqueous solutions separately to 60℃ to 65℃, then mix the two aqueous solutions and react them with stirring for 2 to 3 hours, separating the Mo-doped CuZn basic carbonate and drying it; 2) The dried Mo-doped CuZn basic carbonate was calcined at 200℃~250℃ for 4~5 h to obtain the catalyst precursor; 3) Activate the catalyst precursor in H2 atmosphere, set the activation temperature to 200℃~250℃ and hold for 1~4 h; cool to room temperature to obtain CuZnMo composite catalyst.

2. The application according to claim 1, characterized in that, The molar ratio of copper to zinc is Cu:Zn=1:(0.8-1.1); the molar amount of molybdenum is 0.5% to 1.2% of the sum of the molar amounts of copper and zinc.

3. The application according to claim 2, characterized in that, The molar ratio of copper to zinc is Cu:Zn=1:1; the molar amount of molybdenum is 0.5% to 1.0% of the sum of the molar amounts of copper and zinc.

4. The application according to claim 1, characterized in that, The Cu and Zn metal salts include their metal nitrates, metal sulfates, and metal chlorides; the Mo metal salt is ammonium molybdate.

5. The application according to claim 1, characterized in that, The Cu and Zn metal salts are copper nitrate and zinc nitrate.

6. The application according to any one of claims 1-5, characterized in that, The catalyst is used in the hydrogenation of dimethyl adipate to prepare 1,6-hexanediol, with 1,4-dioxane as solvent, at a reaction temperature of 140℃~180℃ and a hydrogen pressure of 2~5 MPa.

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